Natural fats, such as butter, are a complex mixture of components and comprise, as major constituents, triglycerides, each being an ester of up to three fatty acid moieties and glycerol. The nature of the individual fatty acid moieties differ, depending on the source. Even from a given source, the glycerides can vary significantly from day to day and season to season. Such variability presents difficulties to the users, such as bakers, because slight changes in the constituents of a fatty ingredient may have substantial impact upon the quality and properties of the final product. Accordingly, users of such natural fat products must continually adjust formulation and process variables to accommodate such changes in the natural fat sources.
Butter, in general, because of it being an extremely varied and complex mixture of fatty acid glycerides, has indefinite properties and characteristics, such as melting point, which typically occurs over a wide temperature range. The properties and characteristics also vary with seasonal and climatic changes.
Because of such variability, it would be beneficial to have a means of providing various fat products with some degree of uniformity, to obviate the need for the user to continually monitor and adjust processing conditions. In the baking and cooking industry, it is particularly critical to have available fat components that have very narrowly defined properties, such as narrow and well-defined melting points.
Also, it is well recognized that many, if not most, natural fats that find use in consumer foods, contain substantial amounts of saturated fats. Butter is a prime example. For many consumer applications, it would be desirable to reduce the amount of saturated fat in the end product, as by reducing the amount of saturated fat in the initial fat constituent, such as butter. Thus, a general process capable of lowering the amount of saturated fat, when compared with an unprocessed natural product, such as butter, would be desirable.
Although various techniques and processes have been employed to treat natural fatty materials, such as butter, to derive fat fractions with specific characteristics, most such process do more than just alter the components of the material, they also adversely affect quality of the product, especially with respect to its taste, aroma, or texture.
When one considers butter, for example, any processed product to be acceptable to a consumer needs to maintain the flavor and texture of butter. Spreadability upon removal from the refrigerator is also desirable.
Because the saturated fats, in general, have higher melting points than unsaturated fats, through the selective removal of at least a portion of such higher-melting fats, it is possible to make a fat-fraction that is lower in saturated fats, while being spreadable, as the unsaturated fraction has a higher proportion of lower-melting components, making the same spreadable.
A number of commercial processes have been attempted to produce fractions of natural fat compositions with defined properties, as for use in the cooking and baking industry. Such processes have included short path distillation, super-critical extraction and melt crystallization, In general, the processes result in the production of a "hard" fraction containing the high melting fats, and a light fraction containing the low melting materials. When the starting material is butter, the "hard" fraction is useful in baking applications and in shortenings. The light fraction may be employed as butter.
The melt crystallization approach has found the widest acceptance, mainly because of legislative and economic issues. The principal process is known as the "Tirtiaux" process. In accordance with that process, butter is heated to a temperature of about 60.degree. C. to melt the butter. The butter is then cooled at a very low rate of cooling, approximately 3.degree. C. per hour, resulting in the formation of large crystals of fat, approximately 300 microns in size. A wide size distribution of particles 1-600 .mu.m can be expected. The crystals are comprised of high melting components, the liquid being comprised mainly of the low melting component. The liquid phase contains mainly the unsaturated portion of the components. A vacuum bed filter is used to filter out the crystals, unfortunately leaving a significant amount of liquid behind with the crystals. The crystallization cycle takes approximately 20 hours to produce just one fraction from the original butterfat feed, and the entire time necessary to perform two crystallization cycles would be over 60 hours. The butter undergoing such processing also suffers significant degradation in its flavor.
In present-day processes, three steps are traditionally employed. In accordance with the first step, butter is heated and held at 60.degree. C. to remove any previous thermal history. Nucleation and crystal growth is then induced under very closely controlled temperature conditions. This second step is very time consuming and the necessary equipment is capital intensive. This step can take from ten to eighteen hours per fractionation step. The resulting crystals are generally about 300 microns in size. Such large crystals result because of the slow growth caused by the extremely slow cooling, usually about 0.01.degree. c./min. Fast cooling is an anathema to the Tirtiaux process, as fast cooling would result in the formation of small crystals that are difficult to filter and in fluids with very high viscosities, also making filtering and processing difficult. Subjecting the butter to long heat treatment periods can also cause the butter to loose flavor due to vaporization of smaller molecular weight flavor enhancing compounds.
Additionally, the present processing of butter requires a pasteurization step in which the butter is rendered relatively free of bacteria and other organisms. Unfortunately, the higher temperatures needed in the pasteurization process adversely affect the flavor of the butter. Further, even with the use of such high temperatures, the pasteurization process does not eliminate all undesirable bacteria. A need therefore also exists for a means for reducing the bacterial count of butter, without the need for pasteurization.